This invention relates to improvements to adjustable steering column assemblies for vehicles.
Steering column assemblies for automotive vehicles and the like are increasingly required to be adjustable for steering wheel height known as rake and, in many cases, steering wheel distance known as reach. This requires the column shroud, within which the steering column shaft attached to the steering wheel is rotatably located, to be fixed to the vehicle by a clamp mechanism which can be clamped and unclamped to either prevent or permit adjustment of the column shroud position respectively.
A typical adjustable steering column assembly comprises a first shroud portion, a second shroud portion and a clamp mechanism that includes a bracket secured to a fixed part of a vehicle and in which the first and second portions are releasably engaged by the clamp mechanism to selectively permit an amount of relative movement between the first and second portions that is required during adjustment of the steering column assembly. The clamp mechanism can be unclamped and clamped by movement of a locking lever or handle or, sometimes, electrically using a motor or perhaps hydraulically or pneumatically. However the present invention focuses on the lever locking mechanism.
By releasing the clamp mechanism and telescopically sliding the first portion over the second portion the length of the shroud can be altered, altering the reach position of an associated steering wheel. By moving both portions together up and down relative to the clamp mechanism the rake can be adjusted. In some assemblies only one of reach and rake may be adjusted. The clamp mechanism may clamp the shroud to a bracket (known as a support bracket) which is connected to the vehicle. Thus, when the clamp mechanism is clamped the length of the steering column assembly is fixed, and it is prevented from moving due to the rigid connection through the bracket to the vehicle.
The mechanism is clamped by movement of a lever which is generally easily accessible to a user from the driver's seat of a vehicle. However it has been found that the force or effort that must be exerted (by a user of the lever) differs considerably depending on the reach position of the steering column assembly when being clamped.